Method and apparatus for the abatement of toxic gas components from a semiconductor manufacturing process effluent stream

ABSTRACT

An apparatus and process for abating at least one acid or hydride gas component or by-product thereof, from an effluent stream deriving from a semiconductor manufacturing process, comprising, a first sorbent bed material having a high capacity sorbent affinity for the acid or hydride gas component, a second and discreet sorbent bed material having a high capture rate sorbent affinity for the same gas component, and a flow path joining the process in gas flow communication with the sorbent bed materials such that effluent is flowed through the sorbent beds, to reduce the acid or hydride gas component. The first sorbent bed material preferably comprises basic copper carbonate and the second sorbent bed preferably comprises at least one of, CuO, AgO, CoO, CO 3 O 4 , ZnO, MnO 2  and mixtures thereof.

This application is a continuation-in-part of U.S. application Ser. No.10/314,727, filed on Dec. 9, 2002, now U.S. Pat. No. 6,805,728.

BACKGROUND

1. Field of the Invention

The present invention relates to a method and apparatus for removingtoxic gas components exhausted from a semiconductor process using same.

2. Description of the Related Art

In the manufacture of semiconductors, the toxic, flammable, andcorrosive nature of hydride and acid gases pose considerable health andenvironmental hazards in addition to jeopardizing the integrity ofexhaust systems.

Material gases, such as BF₃, AsH₃ and PH₃ are used as primary dopantgases in ion implantation processes. Other gases, such as SiF₄, GeF₄,(hfac)In(CH₃)₂ and Br₂Sb(CH₃) etc. are also used.

In the case of MOVPE/PECVD gases such as SiH₄, SiF₄, NH₃, AsH₃ and PH₃are delivered to a process chamber through electrically isolatedassemblies. AsH₃ or PH₃ are flowed at particularly high rates duringdeposition to provide atomic As or P of GaAs or GaP, respectively. HClcan be flowed over Ga metal in order to provide GaCl as a precursor tothe atomic Ga of GaN. Epitaxial dielectric is deposited from SiH₄.

HCl and HF can be used for chamber cleans by creating radicals in aplasma stream, which flow to areas in the chamber where excess filmaccumulates. The radicals react with the deposited film to creategaseous by-products. The by-products are then removed from the chamberand pumped out as effluent.

Ongoing research focused on reducing emission levels of such toxic gasesfrom the effluent waste streams of semiconductor manufacturingprocesses, involves the optimization of abatement processes. Currentprocesses include a variety of thermal, wet and/or dry scrubbingoperations.

Thermal scrubbers react an oxidizing agent (almost always air) with atarget component (e.g. AsH₃, PH₃, etc.) in a process effluent stream toproduce an oxidized species of the target component (e.g. As₂O₃, P₂0₅,etc.). The oxidized species is then removed from the effluent stream bycontacting the stream with a gas absorption column (water scrubber). Thedisadvantages of such a system are (a) it is energy intensive in that itrequires significant amounts of electricity and/or fuel, such as H₂ orCH₄, (b) it requires water, and (c) it produces an aqueous hazardouswaste stream when it scrubs arsenic containing compounds.

Wet scrubbing of effluent streams involves contacting the effluent gasfrom a specific process with a scrubbing liquid to cause undesiredeffluent stream components to be absorbed by the liquid, or to reactwith the liquid (e.g., a caustic solution for contacting with an acidgas effluent) to effect the removal of the undesired components from thegas phase. Often the scrubbing liquid includes an oxidizing agent suchas potassium permanganate, a regulated substance, or sodiumhypochlorite, which leads to unwanted precipitation reactions. Further,the wet scrubbing system requires the consumption of significant amountsof the oxidizing agents and leads to a contaminated aqueous wastestream.

Dry scrubbing involves contacting the effluent gas with a solid materialwhich functions to chemisorb or react with the undesired components toeffect their removal. Dry scrubbing concentrates and fully containshazardous abated components, is passive in operation, has no movingparts and works on demand, making it the safest and most preferable modeof abatement operation.

With respect to ion implant processes it is expected that fluorinatedacid gases will pass through an ion implant system largely intact, whilehydride source gases will pass through only moderately intact. Thus, thelarge flow-rates of intact acid gas components and the high toxicity andlow levels of permissible personnel exposure of hydride gas components(for example, the threshold limit value (TLV) for AsH₃ is 0.05 ppm, or aIDLH of 3 ppm) mandate highly efficient effluent stream treatment and/orabatement for removal of both gas types.

In addition to the foregoing issues incident to the use and operation ofion implantation systems, empirical characterization of ion implantprocess exhaust streams reveal significant emissions of hazardous gasesin the process system from source gas pumps, roughing pumps and fromcryogenic pump regeneration cycles.

It is important to note that for dry scrubbing purposes, the chemicalrequirements to scrub acid gases such as BF₃ and SiF₄ are entirelydifferent than the chemical requirements to scrub hydride gases such asAsH₃, PH₃ and GeH₄.

With respect to chemical vapor deposition (CVD) processes, an acid gasand/or hydride gas may be used in combination with large amounts of aballast or process gas, (e.g. hydrogen). Dry scrubbing of effluentstreams deriving from such a process is difficult because a secondaryreaction, typically reductive hydrogenation may occur between thescrubbing material and hydrogen at a temperature around 110° C. to 120°C. The secondary reaction, once initiated, may lead to a “runaway”situation, where temperatures in the scrubbing material reach 600° C.

Cupric oxide CuO, cupric hydroxide Cu(OH)₂, and copper carbonate CuCO₃,based materials are used in resin scrubbing materials for abatement ofhydride compounds from semiconductor effluent streams. Although mostcopper based resins react exothermically with hydrides, CuO and Cu(OH)₂,materials can exotherm severely at temperatures between 110° C. to 120°C. in the presence of large quantities of hydrogen.

For example, U.S. Pat. Nos. 4,743,435, 4,910,001 and 4,996,030 disclosemethods for removing hydride gas species from MOCVD applications usingCuO based resins. However, the capacity of CuO based materials islimited due to the copper surface area and when attempts are made toincrease CuO content, most notably by addition of CuO to a metal oxidemixture used to create the resin, the surface area can dropinordinately. Additionally, the material can exotherm severely due tothe heats of adsorption and reaction of the hydride gas and since mostCVD applications use large amounts of H₂ as carrier gas with AsH₃ andPH₃, temperature of the CuO material is critical, as exceeding atemperature of approximately 110° C. to 120° C. may result in thereduction of the CuO material by H₂, thereby creating severe exothermsthat can exceed 500° C. to 600° C.

U.S. Pat. No. 5,853,678 discloses a method of removing harmful,volatile, inorganic hydrides, inorganic halides and organometalliccompounds by contacting the harmful compound with crystalline cuprichydroxide. However, similar to CuO based materials, crystalline cuprichydroxide, Cu(OH)₂, based materials react with hydride gases to undergoH₂ reduction reactions in approximately the same temperature regime asCuO.

Japanese publication JP1996059391A discloses a method of removing GroupV species from effluents containing same by contacting the Group Vspecies with basic copper carbonate CUCO₃·Cu(OH)₂. Basic coppercarbonate undergoes H₂ reduction reactions at temperatures higher thanboth CuO and Cu(OH)₂.

It would therefore be a significant advance in the art, and accordinglyis an object of the present invention, to provide an abatement systemcapable of handling acid, hydride and/or metalorganic gases, whicheliminates or at least ameliorates the aforementioned hazards ofconventional CuO and Cu(OH)₂ processes.

It is another object of the invention to provide an improved system forthe treatment of effluent streams comprising acid, hydride and/ormetalorganic gaseous components having a potential operating temperatureregime that is greater than 100° C.

It is another object of the instant invention to provide a safe,low-cost, high capacity, high efficiency system for the treatment ofeffluent streams comprising acid, hydride, and/or metalorganic gaseouscomponents.

Other objects and advantages will be more fully apparent from theensuing disclosure and appended claims.

SUMMARY

In one aspect, the present invention relates to an apparatus forabatement of at least one toxic gas component or by-product thereof,from an effluent stream deriving from a semiconductor manufacturingprocess, such apparatus comprising:

-   -   a first sorbent bed material having a high surface area and a        physical sorbent affinity for at least one toxic gas component;    -   a second, discreet, sorbent bed material having a high capacity        sorbent affinity for said the at least one toxic gas component;    -   a third, discreet, sorbent bed material having a high capture        rate sorbent affinity for the at least one toxic gas component;        and    -   a flow path joining the process in gas flow communication with        the sorbent bed materials such that the effluent stream contacts        the first sorbent bed material prior to contacting the second        and third sorbent bed materials to at least partially remove the        at least one toxic gas component from the effluent stream.

In a further aspect, the present invention relates to an apparatus forabatement of at least one acid gas, hydride gas or by-product thereof,from an effluent stream deriving from a semiconductor manufacturingprocess, such apparatus comprising:

-   -   a first sorbent bed material having a high surface area and a        physical sorbent affinity for at least one acid gas, hydride gas        or by-product thereof;    -   a second, discreet, sorbent bed material having a high capacity        sorbent affinity for the at least one acid gas, hydride gas or        by-product thereof;    -   a third, discreet, sorbent bed material having a high capture        rate sorbent affinity for said at least one acid gas, hydride        gas or by-product thereof; and    -   a flow path joining the process in gas flow communication with        the sorbent bed materials such that the effluent stream contacts        the first sorbent bed material prior to contact the second and        third sorbent bed materials to at least partially remove the at        least one acid gas, hydride gas or by-product thereof from the        effluent stream.

In a further aspect, the present invention relates to a layered dryresin sorbent system for abatement of an acid gas or hydride gas orby-product thereof, comprising:

-   -   a first sorbent bed material having a high surface area and a        physical sorbent affinity for the at least one acid gas, hydride        gas or by-product thereof;    -   a second, discreet, sorbent bed material having a high capacity        sorbent affinity for the at least one acid or hydride gas        component;    -   a third, discreet, sorbent bed material having a high capture        rate sorbent affinity for the at least one acid or hydride gas        component; and    -   a flow path joining the process in gas flow communication with        the sorbent bed materials such that the effluent stream contacts        the first sorbent bed material prior to the second and third        sorbent bed materials to at least partially remove the at least        one acid gas, hydride gas or by-product thereof from the        effluent stream.

In a still further aspect, the present invention relates to a processfor reducing the concentration of at least one toxic gas component froma semiconductor process effluent stream containing same, said methodcomprising:

-   -   contacting the semiconductor process effluent with first,        second, and third, sorbent composition layers, so as to retain a        portion of the toxic gas component on each of the first, second        and third sorbent composition layers;    -   wherein the first layer comprises a material having a high        surface area and a physical sorbent affinity for the toxic gas        component, the second, sorbent layer comprises a material having        a high sorptive capacity for the toxic component and the third        sorbent layer material comprises a material having a high        capture rate sorptive affinity for the toxic component.

Other aspects and features of the invention will be more fully apparentfrom the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1C show a comparison of different sorbentconfigurations useful in the instant invention.

FIG. 2 is a schematic representation of a sorbent canister unit inaccordance with one embodiment of the present invention.

FIG. 3 is a schematic representation of a chemical vapor depositionscrubber system according to one embodiment of the invention.

FIG. 4 is a schematic representation of a thin film fabrication facilityincluding an effluent abatement system according to one embodiment ofthe present invention.

DETAILED DESCRIPTION

The present invention relates to an apparatus and method for theabatement of toxic gas components present in an effluent gas streamderiving from a semiconductor manufacturing process. More particularlythe present invention relates to an apparatus and method for theabatement of at least one acid or hydride gas component or by-productthereof present in an effluent gas stream from a Group III-Vsemiconductor manufacturing process.

The present invention further relates to an apparatus and method for theabatement of hydride and acid gas components present in an effluent gasstream deriving from a semiconductor manufacturing process, whereextremely high abatement efficiencies are required.

The inventors of the instant invention have discovered that theefficiency of a particular sorbent based abatement system, may beincreased by two to four fold, by placing a layer of a high surface areasorbent bed material having a physical sorbent affinity for a toxic gascomponent, upstream of a of a main bed, high capacity, or high capturerate sorbent material.

In one embodiment, the present invention relates to an apparatus forabatement of at least one toxic gas component or by-product thereof,from an effluent stream deriving from a semiconductor manufacturingprocess, such apparatus comprising:

-   -   a first sorbent bed material having a high surface area and        physical sorbent affinity for trapping the toxic gas component;    -   a second sorbent bed material having a high capacity sorbent        affinity for the at least one toxic gas component;    -   a third and discreet sorbent bed material having a high capture        rate sorbent affinity for the at least one toxic gas component;        and    -   a flow path joining the process in gas flow communication with        the sorbent bed materials such that the effluent stream contacts        the first sorbent bed material prior to the second and third        sorbent bed materials and at least partially removes the at        least one toxic gas component from the effluent stream.

In a preferred embodiment, the semiconductor manufacturing process is aGroup III-V process and the effluent gas stream comprises at least oneacid or hydride gas component or byproduct thereof, which contacts thefirst sorbent bed prior to contacting the second and third sorbent beds.

Semiconductor manufacturing processes frequently employing acid, hydrideand/or metalorganic gaseous components include ion implant, metalorganicchemical vapor deposition (MOCVD) and plasma enhanced chemical vapordeposition (PECVD). Typical acid, hydride and/or metalorganic componentsand process by-products, which are consumed and usefully abated in suchprocesses, include but are not limited to, AsH₃, PH₃, SbH₃, BiH₃, GeH₄,SiH₄, NH₃, HF, HCl, HBr, Cl₂, F₂, Br₂, BCl₃, BF₃, AsCI₃, PCI₃, PF₃,GeF₄, AsF ₅, WF₆, SiF₄, SiBr₄, COF₂, OF₂, SO₂, SO₂F₂, SOF₂, WOF4, CIF3(hfac)In(CH₃)₂H₂As(t-butyl), and Br₂Sb(CH₃). Other usefully abatedcomponents include chlorosilanes such as SiHCl₃, and SiH₂Cl₂.

In one embodiment, the apparatus of the present invention comprises alayered dry resin sorbent system for abatement of at least one acid gascomponent, hydride gas component or by-product thereof, from a GroupIII-V semiconductor process of a semiconductor manufacturing facility,comprising:

-   -   a first sorbent bed material having a high surface area,        physical sorbent affinity for trapping the toxic gas component;    -   a second sorbent bed material having a high capacity sorbent        affinity for the at least one acid gas, hydride gas or        by-product component;    -   a third sorbent bed material having a high capture rate sorbent        affinity for the at; and    -   a flow path joining the process in gas flow communication with        the sorbent bed materials such that effluent is flowed through        the sorbent beds, to at least partially remove the at least one        acid, hydride, or byproduct component from the effluent.

The layered sorbent system of the instant invention comprises at leastdiscrete, first, second and third sorbent layers where the second “slow”layer has a mass transfer zone (MTZ) that is greater than the “fast”third sorbent layer as well as a higher intrinsic or theoreticalcapacity.

The sorbent materials of the instant invention may comprise aphysisorbent and/or a chemisorbent, as desired to effect desiredabatement of effluent species.

The following definitions are provided for terms used herein:

-   -   “layer” is defined as a tabular body of sorbent articles, lying        parallel to a supporting surface and distinctly limited above        and below.    -   “TLV” is defined as the threshold limit value of a particular        species and reflects the level of exposure to the particular        species that a typical person can experience without an        unreasonable risk of disease or injury.    -   “TLV sorbent capacity” is defined as the moles of gaseous        component retained by a sorbent material per liter of sorbent        material, when the breakthrough concentration reaches the        species' TLV value;    -   “mass transfer zone” (MTZ) is defined as the length of sorbent        layer required in order to remove a target contaminant (hydride        gas, acid gas and/or byproduct thereof) from its incoming        concentration level to a level defined as the breakthrough level        (i.e. the concentration level at which a sorbent bed requires        change-out, commonly chosen as the TLV of a particular species);    -   “slow” is defined as having a MTZ thickness that is between 25        and 100% of the total thickness of the first sorbent layer; and    -   “fast” is defined as having a MTZ thickness that is less than        the MTZ thickness of the “slow” sorbent layer.

For the “fast” sorbent layer to have a shorter MTZ, the “fast” sorbentlayer material must have a “capture rate” for a particular targetspecies that is higher than that of the “slow” layer material. Thecapture rate is the sum of all rates (e.g. characteristic mass transferrate, gas adsorption rate, and chemical reaction rate of the targetspecies with the sorbent material).

The MTZ thickness of the “slow” sorbent bed layer is intrinsicallythicker than the MTZ of the “fast” sorbent bed layer. The thickness ofthe MTZ for the second sorbent bed layer is preferably between 10 and100% of the total thickness of the second and third layers. Morepreferably, the thickness of the MTZ of the second sorbent bed layer isbetween 25 and 75% of the total thickness of the second and thirdlayers. Most preferably, the thickness of the MTZ of the second sorbentbed is about 50% of the total thickness of the second and third layers.Under certain steady state conditions the thickness of the MTZ of the“slow” sorbent layer may be greater than 100% of the thickness for thesecond and third layers, as the thickness of the MTZ will grow withtime. The long MTZ advantageously helps to diffuse heat evolution, whichoccurs from the chemical reaction between the sorbent material andtarget species.

Layering of the sorbent materials involves the arrangement of placinglayers of at least one high surface area trapping adsorbent upstream ofa “slower” high capacity resin material and both the high surfacetrapping adsorbent and “slower” resin material upstream of at least onelayer of a “faster” high capture rate resin material. The “slower”, highcapacity resin materials typically require longer mass transfer zones(MTZ). Conversely, the “faster” high capture rate resin materials oftenhave a lower sorbent capacity for the target gas, but have high capturerates (shorter MTZ).

The high surface area trapping adsorbent may comprise a singlecomposition or mixture of discreet components. In one embodiment, thetrapping adsorbent comprises a material such as carbon, alumina, silica,diatomaceous earth or zeolite having a high surface area (e.g. between100 to 1000 m²/g).

In one embodiment, the high surface area trapping adsorbent comprisesbetween 10 and 60% of the total sorbent material used in the system, the“slow” sorbent bed material comprises between 20 and 80% and the “fast”sorbent bed material comprises between 5 and 30% of the total sorbentmaterial used in the system. Preferably the high surface area trappingadsorbent comprises between 40 and 60% of system's total sorbentmaterial.

FIGS. 1A through 1C show a comparison of different sorbentconfigurations useful in the instant invention. The threshold limitvalue (TLV) breakthrough for a “slower” high capacity sorbent materialoccurs before much of the sorbent material is consumed (FIG. 1A). Bylayering a “faster” high capture rate sorbent material (FIG. 1B),downstream of a “slower” resin material (FIG. 1C), the TLV is shortenedand a higher percentage of the “slower” resin material is consumed whileachieving high abatement efficiencies.

For the capacity of the “slow” sorbent bed layer to be higher than thecapacity of the “fast” sorbent bed layer the first sorbent bed materialpreferably comprises between 20 to 100 wt % active ingredient.

Preferably, the “slow” sorbent layer comprises a material having asurface area that is less than the surface area of the “fast” sorbentmaterial, making the “slow” sorbent material slower to react with acontaminant species. The surface area of the “slow” sorbent material mayrange from about 5.0 to 300.0 m²/g). Lower surface areas, and slowercapture rates increase the MTZ, which advantageously aids in dispersingheats of reactions.

The MTZ thickness of the “fast” sorbent layer must be less than or equalto the thickness of the MTZ of the “slow” sorbent layer. Such arequirement results in a system having an overall increased capacity. Inone embodiment, the MTZ length of the “fast” sorbent layer is less thanor equal to 90% of the MTZ thickness of the “slow” sorbent layer, morepreferably less than or equal to 50% of the MTZ thickness of the “slow”sorbent layer and most preferably less than or equal to 10% of the MTZthickness of the “slow” sorbent layer.

The “fast” sorbent material may comprise a single composition or mixtureof discreet components. In one embodiment, the “fast” sorbent materialcomprises a base adsorbent such as carbon, alumina, silica, diatomaceousearth or zeolite having a high surface area (e.g. between 100 to 1000m2/g) and an active ingredient impregnated into or coated onto a baseadsorbent. The amount of active ingredient preferably comprises fromabout 0.1 to 100% by weight, more preferably between 0.5 and 50% byweight and most preferably between about 1 and 15% by weight of thetotal weight of the “fast” sorbent material.

The ratio of the percents of “faster” to “slower” sorbent materialsuseful in the present invention is dependent on the chemical andphysical properties of the materials such as surface area, porosity,particles shape, particle size, etc., and may be readily determined byone of ordinary skill in the art. In one embodiment the system of theinstant invention comprises a volumetric ratio of “fast” sorbent layerto “slow” sorbent layer of from about 1:20 to 1:1.

The first, second and third layers may comprise sorbent articles of anysuitable composition, size, shape and conformation appropriate to theend use application and the specific effluent gas mixture involved inthe Group III-V semiconductor process. The sorbent articles may compriseactive ingredients and inactive ingredients, and may be in a finelydivided form, e.g., beads, spheres, rings, toroidal shapes, irregularshapes, rods, cylinders, flakes, films, cubes, polygonal geometricshapes, sheets, fibers, coils, helices, meshes, sintered porous masses,granules, pellets, tablets, powders, particulates, extrudates, cloth orweb form materials, honeycomb matrix monolith, composites (of thesorbent article with other components), or comminuted or crushed formsof the foregoing conformations.

In one embodiment, the sorbent layers comprise particulates having asize range of from about 0.1 mm to 1.5 cm. Preferably, the “slow”sorbent layer comprises particulates having a size range of from about1.0 mm to 15 mm, more preferably from about 0.8 mm to 7.5 mm, and mostpreferably from about 1.5 mm to 5.0 mm and preferably the “fast” sorbentlayer comprises particulates having a size range of from about 0.1 mm to7.5 mm, more preferably from about 0.5 mm to 5.0 mm and most preferablyfrom about 0.5 mm to 4.0 mm.

The sorbent layers may be housed in a single containment system orseparate containment systems. Preferably, the sorbent layers are housedin a single containment system and the effluent stream comprising acidand/or hydride gas components, contacts the first sorbent layer materialprior to contacting the second and third sorbent layer materials.

In one embodiment, the sorbent layers are housed in separate containersand one or more containers comprising at least a first high surface areatrapping adsorbent, and a “slow” sorbent layer are coupled to a separatecontainer or polisher comprising at least one “fast” sorbent layer. Thecontainers comprising the high surface area trapping adsorbent and the“slow” sorbent, may comprise same or similar sorbents capable ofscrubbing same or differing toxic components from an effluent processstream. Further, the containers comprising the high surface areatrapping adsorbent and the “slow” sorbent, may serve the same ordifferent tools. When the high surface area trapping adsorbent and thedual “slow” containers are plumbed to the same process tool,auto-switching capabilities between canisters exists. The polisher mayfurther serve as a back up abatement system for a main abatementapparatus as described herein.

In a further embodiment the overall capacity of the abatement system ismaximized by a cyclical process in which a toxic gas species is firstflowed into and through the system for a set period of time, (e.g. untilthe high surface area trapping adsorbent or any other layer becomesineffective) at which time the ineffective sorbent material is taken offline and regenerated.

The ineffective sorbent material may be regenerated using air, ozone,other oxidizing agent or combinations of the foregoing as well as incombination with N₂ and/or other inert gases. The regeneration stepconverts chemically or physically trapped toxic gas species (e.g.hydride gas species) into non-volatile solids. Such regenerationprovides for reuse of the sorbent material.

In one embodiment, ozone produced by an ozone generator, may be used toregenerate the ineffective sorbent material. More specifically, an ozonegenerator useful in the present invention may function by passing airbetween two concentric tubes, where a high voltage is supplied to onetube so as to create an electrical discharge within annular space of thetube. The discharge electrically excites oxygen in the air whichrecombines to form ozone.

In a further embodiment the capacity of the abatement system may bemaximized by cooling of the high surface area physical sorbent materialand/or cooling of the effluent gas stream upon contacting the first highsurface area physical sorbent material layer.

FIG. 2 is a schematic representation of a sorbent canister unit 200 suchas may be employed for the treatment of Group III-V effluent gases inaccordance with one embodiment of the present invention.

The sorbent canister unit 200 includes a vessel 202 enclosing aninterior vessel volume 204 communicating with the waste gas stream feedpassage 206 in inlet 208, and communicating with the scrubbed gasdischarge passage 210 in outlet 212. At the respective inlet and outletends of the vessel 202 are provided screen or grid members 214 and 216,respectively. These foraminous members serve to contain the bed 211 ofsorbent media in the vessel's interior volume, so that solids attritiondoes not occur in use of the system as waste gas is flowed from theinlet 206 to outlet 212 of the vessel through the bed of sorbent mediatherein.

The bed 211 of sorbent media may comprise a plurality of discrete zonesor layers of different sorbent materials 218 and 220. The sorbentmaterials 218 and 220 may further comprise different materialcompositions, which are blended to provide a uniform mixture or monolithof same.

Thus, different sorbent materials are preferably employed, in discretebed zones or layers wherein such layers may comprise sorbent materials,having different physical affinities for a particular wasted gasspecies. For example, one such material layer 218 may comprise a highcapacity sorbent selective for acid gas components of the effluent gasstream from a process such as ion implantation and/or PECVD, and asecond layer 220, may comprise a high capture rate sorbent, alsoselective for acid gas components in the effluent gas stream.

Further, each layer may comprise a blended mixture of sorbent materials,in which the respective materials are selective for removal of differentwaste gas species. For example, one such sorbent material may be highlyselective for acid gas components of the effluent gas stream, andanother sorbent material may be highly selective for hydride gas speciesin the effluent gas stream.

In a preferred embodiment, the “fast” sorbent layer material comprises acomposition selected from the following compositions in approximateweight percents:

-   -   1. copper oxide, (Cu 6%); Silver oxide, (Ag 0.1%); zinc oxide,        (Zn 6.0%); Molybdenum oxide, (Mo 2.5%); triethylenediamine,        (TEDA 3.5%); and activated carbon; and    -   2. manganese oxide, (Mn 22%); copper oxide, (Cu 23%); cobalt        oxide, (Co 10%); silver oxide (Ag 3.5%); and aluminum oxide, (Al        2.6%).

The composition of the high capture rate “fast” sorbents of the presentinvention are preferably resistant to by-products produced during targetspecies interaction/abatement with the “slow” sorbent layer, includingbut not limited to H₂O and/or CO₂. Preferably the composition of the“fast” sorbent layer comprises at least one active component selectedfrom the group consisting of, carbon, CuO, Cu₂O, MnOx, wherein x is from1 to 2 inclusive, AgO, Ag₂O, CoO, CO₃O₄, Cr₂O₃, CrO₃, MoO₂, MoO₃, TiO₂,NiO, LiOH, Ca(OH)₂, CaO, NaOH, KOH, Fe₂O₃, ZnO, Al₂O₃, K₂CO₃, KHCO₃,Na₂CO₃, NaHCO₃, NH₃OH, Sr(OH)₂, HCOONa, BaOH, KMnO₄, SiO₂, ZnO, MgO,Mg(OH)₂, Na₂O₃S₂, triethylenediamine (TEDA) and mixtures thereof. Morepreferably, the composition of the “fast” sorbent layer comprises atleast one component selected from the group consisting of, CuO, AgO,CoO, CO₃O₄, ZnO, MnO₂ and mixtures thereof. In addition to an activecomponent, the composition of the “fast” sorbent layer, may furthercomprise a stabilizer or the active component may be impregnated into orcoated onto an adsorbent substrate.

The composition of the high capture rate “fast” sorbents of the presentinvention may further comprise a strong base, such as KOH, whichincreases the abatement kinetics of specific sorbents to acid gases.

In a further embodiment, the present invention relates to a postpolishing abatement system comprising a layer of “fast” sorbentmaterial, wherein said layer is positioned downstream from a primaryabatement system which may comprise any one of dry, wet, or thermalabatement systems. Preferably the composition of the “fast” sorbentlayer comprises at least one component selected from the groupconsisting of, carbon, CuO, Cu₂O, MnOx, wherein x is from 1 to 2inclusive, AgO, Ag₂O, CoO, CO₃O₄, Cr₂O₃, CrO₃, MoO₂, MoO₃, TiO₂, NiO,LiOH, Ca(OH)₂, CaO, NaOH, KOH, Fe₂O₃, ZnO, Al₂O₃, K₂CO₃, KHCO₃, Na₂CO₃,NaHCO₃, NH₃OH, Sr(OH)₂, HCOONa, BaOH, KMnO₄, SiO₂, ZnO, MgO, Mg(OH)₂.Na₂O₃S₂, triethylenediamine (TEDA) and mixtures thereof. Morepreferably, the composition of the “fast” sorbent layer comprises atleast one component selected from the group consisting of, CuO, AgO,CoO, CO₃O₄, ZnO, MnO₂ and mixtures thereof.

Table 1 below shows a comparison of dry resin abatement systems with andwithout a downstream “fast” sorbent polishing system employed.Concentration of target species constituent and linear velocity areidentified in Columns 4 and 5 respectively. In all cases, the polishinglayer increases the TLV capacity of the target species constituent. Theinstant invention provides a means by which to increases TLV capacitiesfor particular gaseous components by as much 100% (See Test numbers 12and 13 below).

TABLE 1 Comparison of Various Compositions Useful in the Dual LayerSystem of the Instant Invention. Polishing Layer Layer 1 “Fast” “Slow”Main Linear Velocity TLV Capacity Test # (Main constituent) ConstituentsConcentration cm/s mol/L (L/kg) 1 CuO/ZnO/KOH NA 0.8% AsH₃ 4 1.16 (20.0)2 CuO/ZnO/KOH CuO, MnO₂ 0.8% AsH₃ 4 1.97 (36.4) 3 CuO/ZnO/KOH NA   3%AsH₃ 2 1.89 (21.4) 4 CuO/ZnO/KOH NA   4% AsH₃ 4 1.16 (20.0) 5CuO/ZnO/KOH NA   2% AsH₃ 4 1.05 (18.1) 6 CuO/ZnO/KOH NA   4% AsH₃ 2 1.60(27.8) 7 CuO/ZnO/KOH NA   1% AsH₃ 4 0.85 (14.7) 8 CuO/ZnO/KOH CuO, MnO₂  4% AsH₃ 4 1.75 (32.3) 9 CuO/ZnO/KOH NA  50% AsH₃ 0.5  4.6 (79.3) 10CuO/ZnO/KOH CuO, MnO₂,  50% AsH₃ 0.5  6.0 (110.7) Co₃O₄, AgO 11CuO/ZnO/KOH NA   1% AsH₃ 1 1.94 (33.2) 12 CuCO₃•CU(OH)₂ NA   4% AsH₃ 41.00 (26.4) 13 CuCO₃•CU(OH)₂ Activated   4% AsH₃ 4 2.04 (56.7) carbon w/metals 14 CuCO₃•CU(OH)₂ Activated  50% AsH₃ 0.5 5.23 (145.4) Carbon w/metals 15 CuCO₃•CU(OH)₂ Ni   4% AsH₃ 4 0.94 (26.2) 16 CuCO₃•CU(OH)₂ CuO,MnO₂,   1% AsH₃ 1 3.67 (102) Co₃O₄, AgO 17 CuCO₃•CU(OH)₂ Activated   4%(PH₃) 1 3.39 (94.2) Carbon w/ metals 18 CuCO₃•CU(OH)₂ Activated   4%AsH₃ 4 2.49 (69.2) Carbon w/ metals and TEDA 19 CuCO₃•CU(OH)₂ NA   2%SiH₄ 1 0.87 (22.9) 20 CuCO₃•CU(OH)₂ Activated   2% SiH₄ 1 1.17 (34.9)Carbon w/ metals and TEDA 21 CuCO₃•CU(OH)₂ Activated   1% SiH₄ 1 2.22(61.4) Carbon w/ metals and TEDA

It will be appreciated that the optimal amount of polish will be basedupon the ratio of the mass transfer zone to the overall length of thesorbent beds, (MTZ/LOB). That is, the relative length of the masstransfer zone within the main resin bed will dictate the optimal amountof polish to use.

FIG. 3 shows a plot of TLV capacity as a function of “fast” sorbentpolishing layer thickness for an abatement system employing basic coppercarbonate, CuCO₃.Cu(OH)₂ as the main bed “slow” sorbent system. Asshown, the optimal polishing layer thickness is approximately 25-30% ofthe total bed length, for a 7 to 9 inches total bed height. As the bedheight increases, the optimal polish amount decreases as a fraction oftotal bed volume.

In a further embodiment the present invention comprises a layered dryresin sorbent system for abatement of an acid gas, hydride gas and/orby-product thereof, from a Group III-V semiconductor process of asemiconductor manufacturing facility, said layered sorbent systemcomprising, a first layer of “slow” sorbent material having acomposition consisting essentially of basic copper carbonate and, asecond layer of “fast” sorbent material having a composition consistingessentially of copper oxide, (Cu 6%); Silver oxide, (Ag 0.1%); zincoxide, (Zn 6.0%); Molybdenum oxide, (Mo 2.5%); triethylenediamine, (TEDA3.5%); and activated carbon, said sorbent system having a TLV sorbentcapacity for arsine at 1 cm/sec of 3.67 moles/liter resin or 102 litersAsH₃/kg resin.

In an alternative embodiment, the present invention comprises a layereddry resin sorbent system for abatement of at least one acid gascomponent, hydride gas component or by-product thereof, from a GroupIII-V semiconductor process of a semiconductor manufacturing facility,comprising:

-   -   a first layer of sorbent bed material having a physical sorbent        affinity for said at least one acid gas, hydride gas or        by-product thereof;    -   a second and discreet layer of sorbent bed material having a        high capacity sorbent affinity for said at least one acid gas,        hydride gas or by-product component; and    -   a third and discreet layer of sorbent bed material having a high        capture rate sorbent affinity for said at least one acid gas,        hydride gas or by-product component; and    -   a flow path joining the process in gas flow communication with        the sorbent bed layers such that effluent is flowed through the        sorbent bed layers, to at least partially remove said at least        one acid, hydride, or byproduct component from the effluent.

The sequential flowing of an effluent gas stream comprising acid orhydride gas components through such a layered configuration, results ina system having a higher capacity for removal of gaseous species due toa synergy effect from the physical and chemical adsorbent phenomena ofthe layered materials.

In such embodiment, the first sorbent bed layer may comprise a highsurface area material for trapping or physisorbing the acid or hydridegas component from the effluent stream. Specific examples of usefultrapping materials included but are not limited to, with the first layerAs a still further alternative, successive vessels may be deployedthrough which the effluent is sequentially flowed, with the main hydridechemisorbent bed being in a first sorbent vessel, the potassiumhydroxide-impregnated material being in a second sorbent vessel, and thehydride chemisorbent, as employed for polishing of the effluent toensure high hydride removal, being in a third sorbent vessel. Each ofthe respective sorbent vessels in multi-vessel arrangements of theinvention can be of a same or different character, and each bed may besized and constructed for optimal chemisorption operation, with respectto bed diameter, bed height, particle size, bed void volume, allowablepressure drop, temperature, pressure, flow rate, etc., by designtechniques well-known to those skilled in the chemisorbent and effluentabatement art.

Such a configuration effectively utilizes synergistic effects of bothphysical and chemical phenomena.

In a further embodiment, a system of the present invention may comprisetwo beds in parallel, wherein each bed comprises a first layer ofsorbent bed material having a high surface area physical sorbentaffinity for a toxic gas component; a second and discreet layer ofsorbent bed material having a high capacity sorbent affinity for saidthe toxic gas component; and a third and discreet layer of sorbent bedmaterial having a high capture rate sorbent affinity for the toxic gascomponent. While one bed is active and contacted with toxic gascomponent, the second bed is regenerated with an oxidizing species, asdiscussed hereinabove. The thickness of the high surface area sorbentlayer may be determined based on the frequency at which the regenerationstep occurs.

In a further embodiment the present invention relates to a process forreducing the concentration of at least one hydride gas, acid gas orby-product species from a Group III-V semiconductor process effluentstream containing same, said method comprising:

-   -   contacting said semiconductor process effluent with a first        sorbent layer composition so as to retain at least a portion of        the gaseous species therein; and    -   contacting said process effluent with a second layer sorbent        composition, so as to retain a second portion of the gaseous        species therein,    -   wherein said first sorbent layer comprises a material having a        high sorptive capacity for said gaseous species and said second        sorbent layer material comprises a material having a high        capture rate sorptive affinity for the gaseous species.        Preferably, the process enables a system having a capacity to        retain a particular gaseous species greater than the sum of the        capacities of the individual sorbent layers.

More specifically, the present invention relates to a method ofdecreasing the concentration of at least one hydride or acid gas speciesfrom a semiconductor manufacturing process effluent gas streamcomprising same, by contacting the at least one gaseous component with afirst solid phase sorbent material comprising at least one of copperoxide, copper hydroxide and basic copper carbonate so as to produce aneffluent gas stream having a reduced concentration of gaseous species;and contacting said effluent gas stream having a reduced concentrationof gaseous species with a second solid phase sorbent material comprisingat least copper oxide, so as to produce an effluent gas stream having aconcentration of gaseous species that is less than the TLV for the atleast one hydride or acid gas species (e.g. 50 ppb for arsine).

In a further embodiment the present invention relates to a high capacitysystem for Group III-V process abatement management comprising dualcanisters, wherein one canister is online and one is offline andavailable for auto-switching when canister one reaches a predeterminedcapacity, said system comprising a layered dry resin sorbent system forabatement of an acid gas, hydride gas and/or by-product thereof, from aGroup III-V semiconductor process of a semiconductor manufacturingfacility, said layered sorbent system comprising, a first layer of“slow” sorbent material and, a second layer of “fast” sorbent material.

The present invention provides for multi-tool effluent abatement ofGroup III-V processes, wherein from one to four process tools arecombined into a single abatement system for removal of gaseous GroupIII-V species from a Group III-V semiconductor process effluent stream.

For ease of reference in the ensuing discussion, a generalizeddescription is set out below of FIG. 4, showing a schematicrepresentation of a thin film fabrication facility 400 including aneffluent abatement system 402 according to one embodiment of the presentinvention.

As used herein, the sorbent compositions herein disclosed are intendedto be broadly construed, and may alternatively comprise, consist, orconsist essentially of the specific stated components or ingredientshereafter specifically identified for such compositions. It will also beunderstood that such compositions may if desired be devoid of componentsor ingredients not herein expressly identified.

The system accommodates the collection of un-utilized acid and hydridegases and their by-products in an effluent gas stream by irreversiblechemisorption, by contacting the effluent gas stream with a chemisorbentcomposition, and the continuous monitoring of the chemisorbent scrubbercomposition to determine the approach to exhaustion of the capacity ofthe chemisorbent scrubber composition to remove undesired components ofthe effluent gas stream.

The chemical vapor deposition (CVD) system includes a feed source 404 ofsource gas for chemical vapor deposition operation, which may comprise asource gas storage and dispensing vessel containing a deposition gassuch as AsH₃ (not shown). From the vessel, gas source flows in line 406to the gas dispensing manifold assembly 408 including line 424, throughwhich the dispensed gas is flowed to the chemical vapor depositionapparatus 426. Concurrently, if desired, a carrier gas, such as argon,helium, hydrogen, etc., is flowed from the carrier gas source 420 inline 422 to the dispensing manifold assembly 408. The carrier gas thusentrains the gas source and forms a gas source mixture.

The gas source mixture flows in line 424 from dispensing manifoldassembly 408 to the CVD reactor 426, being dispersed in the interiorvolume of the reactor. This gaseous source mixture thereby is directedto and impinges on a wafer substrate 432 positioned on susceptor 434heated by heating element 436. The wafer substrate is maintained at asufficiently elevated temperature to cause decomposition of theprecursor vapor mixture and chemical vapor deposition of the desiredcomponent of the precursor on the surface of the wafer substrate.

An effluent comprising waste gases and decomposition by-products isdischarged from the reactor 426 and flows in line 438 to the effluentabatement system 402, comprising a layered sorbent system 444, ofsorbent materials which may include physical adsorbent(s) and/orchemisorbent(s), for removal therein of contaminant(s) and discharge ofa purified effluent gas stream in line 446 to downstream processing orfinal disposition of same.

Effluent gas from the chemical vapor deposition reactor 426 may also bedischarged into a second line 468 and flowed to the abatement system 402comprising a second layered sorbent system 452, for removal of undesiredgas stream components therein, to yield a purified gas stream which isdischarged from the abatement system in line 448 and passed to furthertreatment or other disposition steps.

The abatement system 402 may be provided in duplicate as shown, with oneof the systems being a backup scrubbing and/or by-pass unit, and withthe lines 438 and 468 containing suitable valving and instrumentation toaccommodate such redundancy function, so that one of the beds isinitially on-stream and actively scrubbing the effluent gas stream fromthe chemical vapor deposition reactor 426, while the other is instand-by mode.

At the outlet end of the sorbent beds 444 and 452, effluent tap lines460 and 464, which conveys a side-stream of the effluent gas to anendpoint detector 462, as hereinafter more fully described.

The endpoint detector 462, upon detecting the breakthrough or incipientbreakthrough of one or more species in the effluent being monitored,generates a control signal that is transmitted in transmission line 464to the central processing unit (CPU) 466, which may be operativelyarranged to effect a corresponding action in the facility.

For example, the system may be arranged so that on incipientbreakthrough detection by the endpoint detector, the effluent flow isdiverted to a second sorbent bed, or to a holding (surge) vessel forretention until the regeneration of the sorbent bed has been carriedout.

Alternatively, or additionally, such endpoint breakthrough detection maybe employed to initiate a regeneration sequence, to renew the exhaustedsorbent bed for subsequent on-stream operation.

Alternatively, the two scrubber beds 444 and 452 may be concurrentlyoperated, and may each process different effluent streams generated inthe operation of the chemical vapor deposition apparatus. For example,one of such abatement systems may process a main effluent gas streamfrom the chemical vapor deposition apparatus, while the other may forexample process a minor effluent stream deriving from pump leakage gasin the effluent treatment system.

The abatement system may be deployed as a separate and distinctapparatus component of the overall system, in relation to the chemicalvapor deposition apparatus, and the feed source of the chemical vapordeposition apparatus.

By the system shown in FIG. 4, the process gases leaving the chemicalvapor deposition apparatus (e.g., the chemical vapor depositionchamber), are exhausted to vessel(s) containing at least two dryscrubbing sorbent compositions in discrete layers, specific to thechemical vapor deposition gases to be abated in the effluent gas stream.The dry scrubbing compositions remove the waste gases from effluent,(e.g., the chemical vapor deposition chamber exhaust), by chemisorption,irreversibly bonding the waste gas species to the scrubbing medium tomaximum operator safety and environmental acceptability of the finallydischarged process effluent after its scrubbing treatment.

The features and layout of the semiconductor manufacturing facilityshown in FIG. 1 are illustrative in character only, and any othersuitable features, arrangements and operation may be advantageouslyemployed.

The dry scrubbing sorbent compositions may therefore be provided incanisters, which are deployed in close proximity to treat the effluentgas stream(s) produced by the process and yield an environmentallyacceptable discharged stream. Such canisters can be readily changed outby decoupling same from connecting piping and valving employingconventional connector devices, and replacing the canister of spentsorbent medium with a corresponding canister of fresh medium.

The amount of scrubbing medium used in such disposable canisters forwaste gas treatment will be determined by the available dead volumewithin a particular process tool. With respect to chemical vapordeposition and/or ion implantation, when the canisters are interiorlypositioned in the system housing or exteriorly positioned in closeproximity to the system housing, the amount of scrubbing medium usedwill be determined by the deliverable capacity of the feed source ofdoping gas for the particular system. The feed source volume may bedesirably matched to the system throughput, so that the capacity of thesource gas vessel does not exceed the removal capacity of the waste gasabatement canister(s) deployed in the system.

Although illustratively shown as comprising a two canister unit, theabatement system may in fact be a multiple bed arrangement comprisingmultiple sorbent beds variously connected in series, layers, bypassand/or parallel (manifolded) arrangements.

The features, aspects, and advantages of the present invention are morefully shown with reference to the following non-limiting example.

EXAMPLE

A refers to “slow” sorbent bed material and “P” refers to high surfacearea trapping adsorbent when preceding “A” and “fast” polishing resinmaterial when following “A”.

Experimental Setup:

-   -   a) All tests were performed using a test cell having dimensions        2 inch OD (1.87 inch ID) and approximately 12-inch height.    -   b) The test cell material was stainless steel 304. The cell was        insulated with a layer of 1 inch thick fiberglass.    -   c) To monitor temperature, a 5-pt thermocouple was placed down        the center of the cell.    -   d) The total adsorbent bed height was always 8 inches.    -   e) The ballast gas stream was a mixture containing H₂ and N₂ in        a proportion of 80%/20%, respectively.    -   f) All tests were performed using arsine gas.    -   g) When more than one adsorbent was used, it was layered and not        mixed.    -   h) In the Table below, the adsorbent order reflects the pathway        in which the gas passes through the bed.

TABLE 2 Comparison of Various Compositions Useful in the Multi LayerSystem of the Instant Invention. Adsorbent Test AsH3 Gas Linear CapacityTest # Class Adsorbent Concentration (%) Velocity (cm/sec) (moles/liter)1 I 100% A 2 2 2.18 2 II  80% A, 20% P 2 2 4.65 3 II  80% A, 20% P 2 25.54 4 II  80% A, 20% P 2 2 5.71 5 II  80% A, 20% P 2 2 5.02 6 II  80%A, 20% P 2 2 5.54 7 II  80% A, 20% P 2 2 5.54 8 II  80% A, 20% P 2 24.98 9 II  80% A, 20% P 3 2 5.26 10 II  80% A, 20% P 3 1 4.66 11 II  80%A, 20% P 4 1 3.94 12 II  80% A, 20% P 1 2 4.43 13 III 100% P 1 1 0.79 14III 100% P 2 1 0.97 15 III 100% P 4 1 1.15 16 III 100% P 2 2 0.83 17 IV100% P 2 2 4.30 18 IV  80% A, 20% P 3 1 7.64 19 V 100% P 2 2 4.33 20 V 50% P, 30% A, 20% P 2 2 7.62

RESULTS

Test No. 1; Test Class I, shows using 100% “A” gives poor results due tothe long mass transfer zone of the material.

Test No.s 2-12; Test Class II, shows replacing the top 20% of “A” with“P” yields improved results for a variety of conditions where “P”effectively scavenges small concentrations of bleed-through from layer“A”.

Test No.s 13-16; Test Class III, shows poor results using 100% “P”, dueto low intrinsic capacity of “P”.

Test No.s 17-18; Test Class IV were performed using the followingprocedure:

-   -   (a) arsine run until TLV breakthrough;    -   (b) adsorbent is regenerated using a stream containing about 4%        O₂ in N₂ (although the O2 concentration could be lower or        higher);    -   (c) after regeneration, arsine is again flowed to the adsorbent        until TLV break-through is achieved.

The cycle is repeated until the adsorbent has a small fraction of itsoriginal (1st cycle) capacity. Regeneration works by driving anintermediate compound (e.g. Cu₃As) to As₂O₃ and the metal oxide. Themetal oxide can then re-react with arsine during the subsequent cycle.

Test No.s 19-20; Class V shows a variation of the instant inventionwhere instead of allowing each cycle to proceed to TLV breakthrough, theadsorbent is regenerated after a shorter time period, (e.g. 10-50% ofthe estimated TLV break-through time), which allows for repeated use ofmaterial in the first half of the bed.

It is believed that arsine flowing into the bed, physically adsorbs onthe surface (in the first half of the bed), which during air oxidation(regeneration), converts to As₂O₃. When the first half of the bed actsas a physical adsorbent, some concentration of arsine passes onto thesecond half of the bed. For this reason, the second half of the bed iscomposed of a high capacity material (e.g. material “A”) followed byfast polishing agent (e.g. material “P”).

Test 19 (adsorbent was 100% “P”) shows similar results to Test 17, whereTLV break-through was achieved in each cycle).

Test 20 shows improved results, approximately the same as Test 18, byadding 30% “A” to the second half of the bed. However the cost of theadsorbent bed as a whole decreases significantly because material “A”(and others like it) may cost/liter around $30, whereas “P” may costapproximately $10/liter. The economics are further expanded upon in thefollowing non-limiting example.

Test 18:

-   Cost of Adsorbent=0.8*30+0.2*10=$26/liter-   Cost to treat arsine=$26/liter/7.64 moles arsine/liter=$3.40/mol    arsine

Test 20

-   Cost of Adsorbent=0.3*30+0.7*10=$16/liter-   Cost to treat arsine=$16/liter/7.62 moles arsine/liter=$2.10/mol    arsine-   This method may reduce cost by 38%.

While the invention has been described herein with reference to specificfeatures and illustrative embodiments, it will be recognized that theutility of the invention is not thus limited, but rather extends to andencompasses other features, modifications and alternative embodiments aswill readily suggest themselves to those of ordinary skill in the artbased on the disclosure and illustrative teachings herein. The claimsthat follow are therefore to be construed and interpreted as includingall such features, modifications and alternative embodiments withintheir spirit and scope.

1. An apparatus for abatement of at least one toxic gas component orby-product thereof, from an effluent stream deriving from asemiconductor manufacturing process, such apparatus comprising: a firstsorbent bed material having a high surface area and a physical sorbentaffinity for trapping the at least one toxic gas component; a seconddiscrete sorbent bed material having a high capacity sorbent affinityfor the at least one toxic gas component; a third discrete sorbent bedmaterial having a high capture rate sorbent affinity for the at leastone toxic gas component; and a flow path joining the process in gas flowcommunication with the sorbent bed materials such that the effluentstream contacts the first sorbent bed material then the second and thirdsorbent bed materials to at least partially remove the at least onetoxic gas component from the effluent stream.
 2. The apparatus of claim1, wherein the second sorbent bed material has a mass transfer zone thatis greater than the mass transfer zone of the third sorbent bedmaterial.
 3. The apparatus of claim 1, wherein the first, second andthird sorbent bed materials are arranged in respective first, second andthird layers.
 4. The apparatus of claim 3, wherein the first, second andthird sorbent materials in the respective first, second and third layerseach have different physical affinities for a waste gas species.